In order to cope with the rise in bitrate of optical transmission systems, the limits of wavelength-multiplexing technology (WDM for Wavelength Division Multiplexing in English) have been regularly pushed back.
Over long distances, in order for the bitrate to be able to reach 100 Gbit/s per wavelength, or indeed go beyond this threshold, it is possible to multiplex components at 10 Gbit/s (using 10 GbEthernet technology) so as to obtain an ultra high-bitrate channel at 100 Gbit/s (using 100 GbEthernet technology).
The need to easily deaggregate or aggregate such components in a WDM channel during transmission becomes essential so as to allow a high degree of flexibility in ultra high-bitrate optical transport networks. This deaggregation is beneficial both in terms of cost and energy consumption only on condition that it is wholly optical.
The modulation formats that can be used initially at 100 Gbit/s are based on a single-carrier modulation technique (termed coherent QPSK) which is not well adapted to intra-channel optical switching.
It is also possible to use orthogonal frequency multiplexing (OFDM for Orthogonal Frequency Division Multiplexing in English). This type of multiplexing is a multi-carrier modulation technique which may be implemented using one or more subbands carrying the bitrate of the WDM channel.
Thus, on account of its multi-band approach, OFDM multiplexing is the ideal candidate for implementing intra-channel optical switching making it possible to easily deaggregate or aggregate, in the actual interior of a WDM channel, the independent OFDM subbands.
However, to our knowledge, no device currently exists which makes it possible to extract or to insert an optical subband from or into an optical channel composed of several multiplexed optical subbands.